Acrylonitrile-butadiene copolymer rubber, commonly referred to as nitrile or NBR rubber, is well recognized for its outstanding oil resistance and hence its excellent performance in seal applications where it is necessary to prevent the passage of oil or other fluid from one compartment to another in a given device. For example, ball bearings or other components surrounding a shaft or axle are typically enclosed within a housing that contains oil, grease, or other lubricant fluid. The lubricant fluid is typically sealed within the housing with a metal ring or cylinder which is lined with an elastomeric material such as nitrile rubber. The seal prevents leakage of the lubricant fluid and prevents contaminants from entering the housing.
In order for nitrile rubber to be utilized in seal applications, the nitrile rubber is typically adhesively bonded to a metal ting, cylinder, or the like. The nitrile rubber is typically bonded to the metal ting or cylinder by applying an adhesive to the ring or cylinder and compression molding, transfer molding, injection molding, or autoclave molding the nitrile rubber to the ring or cylinder at temperatures ranging from 175.degree. C. to 200.degree. C. The resulting rubber-lined ting or cylinder is then used in combination with a shaft or axle to form the fluid-tight seal.
Previous adhesive compositions utilized for bonding nitrile rubber are based on organic solvents and hence are becoming more and more undesirable in light of the increasingly circumscribing environmental regulations relating to volatile organic solvents. Many of the previous adhesive compositions have also been found to be adversely affected by the high-bonding temperature (175.degree. C. to 200.degree. C.) which can cause premature degradation of the adhesive, resulting in susceptibility to corrosion at the adhesive-metal interface.
A need therefore exists for an environmentally acceptable aqueous adhesive composition for bonding nitfile rubber that can withstand high temperature bonding conditions. Such an adhesive composition should be capable of being applied as a one-coat formulation and should also be capable of forming an adhesive bond that can withstand adverse environments such as corrosive materials and high temperature fluids.